The present invention relates broadly to directional valves for controlling the flow of a fluid in a fluid power system, and more particularly to a 3-way, 2-position xe2x80x9cbuttonxe2x80x9d valve of such type which is particularly adapted for use in a pneumatic circuit for controlling the operation of a cylinder or other fluid power component.
As is shown, for example, in U.S. Pat. Nos. 3,197,172; 3,357,675; 4,196,937; 4,494,572; 4,576,196; 4,915,134; 5,218,999; and 5,409,032, a variety of valve types and styles are known and used in a host of commercial, industrial, mobile, and military applications for controlling the flow of a fluid for the operation of a component in a fluid power circuit. One such type known as a xe2x80x9cbuttonxe2x80x9d valve is often used to control the operation of a cylinder in a pneumatic circuit. Such valves typically are constructed as a panel-mountable body or housing having an internal bore and though which is formed two or more port openings which are coupled in fluid communication. In a three-way, two position variety, three ports are provided, the first and second being connected along a first fluid flow path, and the second and third being coupled along a second fluid flow path. A stem is slidably received within the bore for movement between a first position, which may be defined as a de-actuated, de-energized, or normally-closed position of the valve, closing the first fluid flow path and opening the second, and a second position, which may be defined as an energized, actuated, or open position of the valve opening the first fluid flow path and closing the second. As incorporated into a pneumatic circuit for the control of a cylinder or the like, the first port may be connected to line pressure, with the second port being connected to the cylinder, and the third port being open to the atmosphere as an exhaust.
The stem may extend between a first end portion which is received within the bore of the housing, and an opposite second end portion which is actuable through an open end of the bore. The stem first end portion typically has a first and an axially spaced-apart second annular valve element portion, each of which portions typically is configured to carry an O-ring coaxially-mounted thereover, each of which O-rings may be contacted in a fluid-tight sealing engagement with a corresponding seating surface defined about the housing bore for alternatingly opening and closing a corresponding one of the fluid flow paths. The stem second end portion may be generally configured as a button which is contactible to apply a force to the stem effecting its actuation from its first position to its second position.
Various actuation means may be provided depending upon the requirements of the particular application involved, such means including manual, mechanical, pneumatic, and/or electrical control, but typically are mechanical in form such as a pivotally-mounted lever or other limit or sensor to which a roller may be attached for contact with a control surface. As the roller is contacted by the control surface, the lever is depressed which, in turn, contacts the button end for providing the actuation force moving the stem from its first to its second position. Upon the removal of the actuation force, the stem shifts back to its first position responsive to air or other fluid pressure admitted through the first port to provide an air spring return, with fluid pressure from the cylinder being relieved through the second port for exhaust through the third port.
Valves of the type herein involved are sold commercially by the Pneumatic Division North America of Parker Hannifin Corporation (Richland, Mich.), Clippard USA (Cincinnati, Ohio), Festo Corporation (Hauppauge, N.Y.), IMI Norgren Inc. (Littleton, Colo.), and Pneumadyne Inc. Plymouth, Minn.). These valves and others have proved satisfactory for a diversity of uses, and heretofore have constituted the state of the art. It is believed, however, that improvements in the construction and operation of such valves would be well-received for use in a variety of fields and applications. In this regard, it is believed a preferred construction would be operable at a reduced actuation force and would require a lower shift back pressure for return.
The present invention is directed, broadly, to directional control valves for controlling the flow of a fluid in a fluid power system. More particularly, the invention is directed to an improved 3-way, 2-position xe2x80x9cbuttonxe2x80x9d valve construction of such type which is particularly adapted for use in a pneumatic circuit for controlling the operation of a cylinder or other fluid power component.
In the valve construction of the invention, a second annular seal element which controls the opening and closing of the second fluid flow path through the valve has an inner diametric extent which is formed, or which is deformed as mounted on the stem end portion, to exhibit an inner lobe portion located inwardly of the midline of the seal element which effects a seal of a given effective sealing diameter with the corresponding seating surface. As compared to a seal conventionally effected with an O-ring, the seal produced by the lobed seal element of the present invention is of a reduced effective diameter which, in turn, results in a corresponding reduction of the actuation force required to effect a seal. Moreover, by employing a seal element having an outer lobe which together with an outer lateral surface which surrounds the seating surface defines a portion of the second fluid flow path therebetween, the effective area of such flow path portion may be minimized with a corresponding reduction in flow and pressure decay through the first fluid flow path as the valve shifts from its first to its second position. Such reduction allows the valve to be shifted at a reduced pressure as compared to valves which employ a conventional O-ring which does not serve to minimize the clearance between the outer diameter thereof and the surrounding lateral surface.
The present invention, accordingly, comprises the arrangement possessing the construction, combination of elements, and arrangement of parts which are exemplified in the detailed disclosure to follow. Advantages of the invention include a valve construction which is economical to manufacture, but which is operable at a reduced actuation force and which requires reduced shift back pressure for its air or other fluid pressure spring return. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.